The present invention relates to a battery pack containing a CPU and allowing correction of measured data.
In the normal CPU control performed in a battery pack containing a CPU (one-chip microcomputer), data concerning the cell voltage, charge/discharge current and temperature is obtained by measurement to control charging and discharging and to perform cumulative calculation of the remaining battery capacity. To increase the accuracy of measurement of the voltage, current and temperature, the conventional practice is to increase the accuracy of a resistor, an amplifier and other components used in the peripheral circuit and to minimize variations from product to product. Accordingly, it has heretofore been necessary to use high-precision and costly components. Consequently, the unit cost increases, and the battery pack itself becomes unfavorably costly.
The present invention was made to solve the above-described problems. Accordingly, an object of the present invention is to provide a battery pack in which data concerning the cell voltage, charge/discharge current and temperature is corrected so that the measurement accuracy can be increased even if low-cost members are used, thereby allowing the costs to be reduced.
To attain the above-described object, the present invention provides a battery pack containing a CPU and allowing correction of measured data. The CPU has, at least, a main program for obtaining data concerning the voltage of each cell, charge/discharge current and temperature by measurement to control charging and discharging and to perform cumulative calculation of the remaining battery capacity, a communication program for communicating with an external device, and a correction program for acquiring measured data to obtain a correction factor for calculating a predetermined value from each item of the measured data and for storing the correction factor in a memory. After the state of each cell has been set to a predetermined value, the correction program is started to obtain a correction factor and to store it in the memory. The main program corrects each item of measured data concerning the cell voltage, charge/discharge current and temperature by the correction factor to control charging and discharging and to perform cumulative calculation of the remaining battery capacity.
The correction program judges whether or not the correction factor obtained is within a predetermined range, and stores the correction factor in the memory on condition that the correction factor is within the predetermined range. The correction program has an initial value for the correction factor and stores the initial value in the memory when a correction factor cannot be obtained by the correction program, or when the correction factor obtained is not within a predetermined range. The correction program outputs error information to the outside when the correction factor obtained is not within the predetermined range. The correction program is started when the communication program receives a predetermined command issued from the external device. Alternatively, the correction program is started in response to an operation of an idle port of the CPU.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.